Typically, a compound semiconductor is produced by growing epitaxial layers on a substrate to form n-type and p-type semiconductor layers. The epitaxial layers are processed via chemical, lithographical, etching, evaporating, and grinding processes to form compound semiconductor devices, such as light-emitting diodes. However, packaged devices cannot be operated under high electric current since the thermal conductivity of the substrate for growing epitaxial layers thereon is lower. Thereby, it is unable to achieve high output power and the lifetime may be shortened sharply when subject to weather influence.
Moreover, when bonding process is undertaken, the bonding layers on the substrate and on the epitaxial layers can be made by same kind of material or two different kinds of material. When the bonding layers are made by the same kind of material (for example, GaP bonded with GaP), it is advantageous that the thermal cycle stress is minimized since the thermal expansion coefficient of two bonding layers are the same. However, under this condition, the temperature is required to be at least 500° C. When the bonding layers are made by two different kinds of material (for example, Au bonded with In or Au bonded with Sn) by using interface layer, the required temperature is lower (only about 300° C.). However, under this condition, though the required temperature is only about 300° C., the bonded structure may easily be deformed or curved. Consequently, it may result in decreasing the yield, increasing the internal stress of devices, and reducing the reliability of products.